Subsurface pump unit



June 21, 1966 c. L. ENGLISH SUBSURFACE PUMP UNIT 3 Sheets-Sheet 1 Filed June 29, 1964 INVENTOR. CHA/as-s A Elva/5H June 21, 1966 c. L. ENGLISH SUBSURFACE PUMP UNIT 2 5 0 a0 7- 7- a B 55 mi? 5 a a 2 4/ t A TI k E m 7 7 7 Q 4 s 1 2 e F e V k A n h S J 4 V 5 \A J I Jr 0 24 w m W 0 4 60 7. 7. 2 04 M 2 M 40? H NMHUM WWW 9 55 a, k A z 4 Filed June 29, 1964 I NVENTOR. CHA Q4 55 Lo E/vsusv-l United States Patent 3,256,826 SUBSURFACE PUMP UNIT Charles L. English, 2204 E. 25th Place, Tulsa, Okla. Filed June 29, 1964, Ser. No. 378,654 13 Claims. (Cl. 10346) This invention relates generally to improvements in fluid operated pump units. More particularly, but not by way of limitation, this invention relates to an improved fluid operated pump unit of the type used in pumping oil wells and the like.

The present invention is an improvement over the pump unit disclosed and claimed in my United States Patent No. 3,024,733, issued May 13, 1962.

Many wells that have been drilled do not have suflicient formation pressure to produce the well fluid to the surface. In such instances, it is necessary to provide some extraneous force for lifting or driving the well fluid to the surface where it can be processed. One method used in the past 'has been to place a pump below the surface of the well fluid and connect it with a surface mounted walking beam which actuates the pump by means of rods. Due to the extreme depths of many present day wells, such a method is not practical.

As'a consequence, various types of pump units have been devised that are mounted in the well beneath the surface of the well fluid to drive the fluid to the surface of the ground. Most subsurface units include not only the pump, but also include some form of motor for actuating the pump.

Of the various types of pump unitsconstructed, those incorporating a fluid driven motor for actuating the pump have proved to be the most feasible. Motive power is supplied to fluid driven motors by relatively high pressure fluid carried by a conduit that extends from a surface mounted fluid pump to the fluid motor mounted in the well.

For the most part, fluid driven motors have performed in a satisfactory manner. However, many have been far too 'complex and, consequently, somewhat difficult to maintain. The complexity has also resulted in a relatively high initial cost. Maintenance costs are also very high due to the installation being several thousand feet deep in a well.

Fluid driven motors include a piston arranged for reciprocating movement in a cylinder. The motor piston is connected with a pump piston. The pump and motor must be operated as rapidly as possible and should make I as complete and long a stroke as possible for eflicient pump operation. The length of the stroke is determined by the length of the cylinder..

Accordingly, the piston should be accelerated rapidly, displaced for an essentially complete stroke at high velocity, and then decelenated rapidly as it approaches the end of the cylinder. Also, as little time as possible should be lost in reversing the direction of movement of the piston. Some pump units constructed in the past have attained most of the foregoing desirable features, but many have eventually destroyed themselves due to engagement of the piston with one or both ends of the cylinder. Many pump unit-s previously constructed have proved to be 11nsatisfactory because the piston incorporated therein will hesitate for an extended period before reversal of the direction of movement in the cylinder.

In general, it is the purpose of this invention to provide a pump unit that will attain all the foregoing desired attributes. A pump unit constructed in accordance with this invention comprises a reciprocating, fluid operated motor connected with a single actin-g pump. The motor includes a differential area piston mounted for reciproca- 3,256,826 Patented June 21, 1966 tion in a motor cylinder and connected with a pump piston. The differential area piston incorporates a differential area-main v'alve which is shiftable by fluid pressure to open and close passageways extending through the piston. The arrangement is such that relatively high fluid pressure is continually exerted on a small end of the differential area piston to drive the piston in one direction. Shifting of the main valve causes the high pressure fluid to be directed to the large end of the differential area piston to cause it to move in the opposite direction.

In another aspect, this invention contemplates a fluid motor which includes a differential area piston positioned for reciprocating movement in a motor cylinder. The piston includes first and second mechanically actuated pilot valves and a differential area main valve adapted to be actuated by fluid pressure. The arrangement is such that the first pilot valve is opened upon engagement with one end of the motor cylinder to direct fluid against the main valve, shifting it to a position wherein fluid acts upon the large end of the differential area piston to cause the piston to move toward the other end of the cylinder. The second pilot valve is actuated upon engagement with the other end of the cylinder to cause fluid to act upon the main valve to shift it to a position confining the fluid to the small end of the diifereutial area piston, whereby it is caused to move in the opposite direction.

One object of the invention is to provide an improved pump unit that will operate for an extended period of time with a minimum of maintenance.

Another object of the invention is to provide an improved pump that is relatively simple in construction and inexpensive to manufacture.

A further object of the invention is to provide an improved pump unit incorporating a reciprocating fluid motor that drives the pump at a relatively high velocity during the return stroke.

An additional object of the invention is to provide an improved reciprocating fluid motor that incorporates a pilot valve in each end of the motor piston that require a relatively small EfilllOlll'lt of mechanical force for actuation to cause a reversal in the direction of piston travel.

The foregoing and additional advantages of the invention will become more apparent as the following description is read in conjunction with the accompanying drawings wherein like reference characters denote like parts in all views, and wherein:

FIGS. 1A, 1B and 1C are vertical cross-sectional views of a pump unit constructed in accordance with the invention;

FIG. 2 is a transverse cross-sectional view taken along the line 22 of FIG. 1A;

FIG. 3 is a transverse cross-sectional view taken along the line 3-3 of FIG. 1A;

FIG. 4 is a schematic sectional view of the motor, illustrating the operation of the motor during a power stroke of the pump unit;

FIG. 5 is a view similar to FIG. 4, but showing the motor at the end of the power stroke with the first pilot valve unseated;

FIG. 6 is a view similar to FIG. 5, but showing the differential area main valve shifted to effecta reversal in direction of movement of the motor piston for the return stroke;

FIG. 7 is a schematic sectional view illustrating the operation of the motor at the end of a return stroke with the second pilot valve in the closed position; and,

FIG. 8 is a view similar to FIG. 7, but showing the differential area main valve shifted to effect the beginning 7 of the power stroke.

Referring now to the drawings, and to FIGS. 1A, 1B and 1G in particular, shown therein is a pump unit, generally designated by the reference character 10. As shown, the pump unit includes a fluid motor 12 and a single acting pump 14 interconnected by means of a header 16. The header 16 is connected by threads 18 to a motor cylinder 20 (see FIG. 1B), and with the upper end of a pump cylinder 22 (see FIG. 10) by threads 24. The header 16 has an aperture 26 extending axially therethrough. A flange 28 extends inwardly into the aperture 26, forming a counterbore 30 in the upper portion of the header 16. An upwardly facing shoulder 32 is provided in the header 16 for purposes which will be explained more fully hereinafter. An inlet opening 34 extends through the wall of the header '16 into the counterbore 30*, providing fluid communication with the interior of the motor cylinder 20 from a source of relatively high pressure fluid (not shown). The lower end of the aperture 26 is threaded as shown at 36, and threadedly receives a packing nut 38 (see FIG. 1C). The packing nut 38 provides a means of adjusting the force exerted on a packing 40 which is disposed in the aperture 26 between the packing nut 38 and the inwardly extending flange 28. The purpose of the packing 40 will be explained more fully hereinafter. A fluid outlet opening 42 extends through the wall of the header 16, providing fluid communication with the interior of the pump cylinder 22.

The pump cylinder 22 is threadedly connected at its lower end 44 with a standing valve assembly 46. The standing valve assembly 46 includes a valve body 48 having an opening 50 extending therethrough. The valve body 48 also includes a valve guide member 52 and a valve seat 54 encircling the opening 50. A valve closure member 56 is slidingly disposed in the valve guide member 52 and has an enlarged head portion 58 adapted to sealingly engage the valve seat 54. A valve retaining member 60, having apertures 62 extending therethrough, is retained in the pump 14 between the lower end of the motor cylinder 22 and an upwardly facing shoulder 64 formed in the valve body 48. The arrangement of the standing valve assembly 46 is such that fluid can pass upwardly through the inlet opening 50 into the pump cylinder 22, but is prevented from flowing in the reverse direction by the engagement of the head portion 58 with the valve seat 54. The valve retaining member is provided to prevent the valve closure member 56 from moving out of the valve guide member 52 when in its upper,

or open, position.

A pump piston 66 is slidingly disposed in the pump cylinder 22 and is provided with a plurality of sealing rings 68 which encircle the piston 66 and sealingly engage the inner wall of the pump cylinder 22 to prevent the passage of fluid between the piston 66 and the cylinder 22. A bore 70 extends through the pump piston 66, providing fluid communication therethrough. A chamber 72 permits communication .from the bore 70 into the interior of a tubular extension member 74, sometimes known as a connecting rod. A traveling valve assembly 76 is disposed in the lower end of the bore 70 and is basically similar to the standing valve assembly 46. The traveling valve assembly 76 includes a combination valve seat and valve guide 78 and a valve member 80 slidingly disposed in the valve seat and guide 78 and having an enlarged upper portion 82 which is engageable with the valve seat and guide 78 to prevent flow downwardly through the bore 70.

The tubular extension member 74 extends upwardly from the pump piston 66 through the packing 40 and aperture 26 of the header 16 and is connected to the lower, or small, end 83 of a differential areamotor piston 84 which is slidingly positioned in the motor cylinder 20 (see FIG. 1B). A fluid-tight seal is formed-between the packing 40 and the tubular extension member 74 due to the force applied on the packing 40 by the packing nut 38.

As shown in FIG. 1A, the motor piston 84 is preferably provided with a plurality of annular sealing rings 86 which extend circumferentially about the piston 84 and sealingly engage the inner wall of the motor cylinder 20. A first fluid passageway 88 (FIGS. 1A and 1B) extends through the motor piston 84 from upper, or large, end 90 of the piston 84 and communicates with the interior of the motor cylinder 20 below the rings 86 through an aperture 92 extending through the wall of the piston 84. The first passageway 88 is used in a generic sense to describe a complex passageway which includes a number of small passageways and ports, as will be described. A tubular member 94, which is positioned within the tubular body 85 of the motor piston 84, encircles a portion of the first passageway 88 and, in cooperation with the tubular body 85, provides a second passageway 96 which extends through the motor piston 84 and has its lower end in communication with the interior of the tubular extension member 74. The upper end portion of the tubular member 94 is provided with a plurality of apertures 98 which permit fluid communication from the second passageway 96 into a plurality of apertures 100 which extend through the wall of the piston 84 just above the sealing rings 86. When installed in the tubular body 85 of the piston 84, the tubular member 94 becomes a fixed part thereof. Except for the difliculty of manufacturing and assembly, the tubular member 94 could have been formed as an integral part of the body 85 of the piston 84, rather than as shown. A low pressure valve seat 102 is formed on an upper, inner surface of the tubular member 94 for purposes which will be explained more fully hereinafter.

The upper end 90 of the motor piston 84 is provided with a bushing 104 which is threadedly secured to the piston 84. A valve seat retaining member 106- is positioned in the first passageway 88 between the lower end of the bushing 104 and the upper end of a first pilot valve member 108. The first pilot valve member 108 is prevented from moving downwardly in the motor piston 84 due to the engagement of a shoulder 110 thereon with an upwardly facing shoulder 112 in the motor piston 84. The valve member 108 has a valve seat member 114 disposed in a passageway 1 16 which extends through the first valve member 108. The valve seat member 114 is preferably constructed as a separate member as illustrated in FIG. 1A so that it can be made of highly wear resistant material of maximum wall thickness or can be heat treated without necessitating the heat treating of the entire member 108. Also, the seat member 114 is subjected to most of the wear and, when constructed as a separate member, can be very easily and economically replaced. A valve ball 118 is positioned in the passageway 116 in such a position that it can move toward and away from the seat 114 to open and close the passageway 116. A high pressure valve seat 120 encircles the lower, exterior portion of the first pilot valve member 108, for purposes which will be explained hereinafter. As may be more clearly seen in FIG. 2, the valve member 108 has a generally triangular-shaped exterior which provides for fluid flow around the exterior thereof through the passageways I122 which constitute an upper extension of the first passageway 88.

The valve seat retaining member 106 is provided with an interior flange 124 which is arranged to engage the upper end of the valve seat member 114 to prevent movement of the valve seat member 114 out of the first pilot valve member 108. Openings 126 are provided in the valve seat retaining member 1 06 and are in communication with the passageways 122 previously described. A valve actuating member 128 is slidingly disposed in the bushing 104 and has an upper portion 130 extending through an aperture 132 in the bushing 104. A lower, stem-like portion 134 of the valve actuating member 128 extends downwardly through an opening 136 in the valve seat retaining member 106 and is engageable with the valve ball 118 to move the ball off the seat member 114. An opening 138 extending through the valve actuating member 128 completes the flow passageway 88 into the interior of the motor cylinder 20 above the piston sealing rings 86. A spring member 140 may be disposed between the valve actuating member 128 andthe valve seat retaining member 106 in such a position that it biases the valve actuating member 128 upwardly away from the valve ball 118. However, the actuating memher 118 is normally held up by pressure differential and the spring member 140 may be omitted if desired. A cover member 142 is threadedly engaged with the upper end of the motor cylinder 20 to completely close the upper end of the motor cylinder.

The lower, or small, end 83 of the motor piston 84 is connected with the tubular extension member 74, as previously described. While the small end 83 of the motor piston 84 is not dimensionally smaller than the upper, or larger, end 90, the end 83 is effectively smaller because the area of the tubular extension member 74 which extends through the packing 40 must be subtracted when computing the effect of fluid pressure acting on the respective ends 83 and 90 of the piston 84. The extreme lower end portion 146 of the small end 83 is arranged to fit closely within the counterbore 30 in the header 16 as the piston 84 moves downwardly in the motor cylinder 20.. The counterbore 30 and the lower end portion 146 of the piston 84 cooperate to act as a dashpot and to restrict the flow of relatively high pressure fluid through the inlet port 34 to reduce the velocity of the piston 84 as it moves toward the header 16, thereby preventing damage which would result from a high velocity impact therewith.

A sleeve 148 is slidingly positioned within the tubular member 94 and is arranged to encircle an upper portion 150 of a second pilot valve member 152. As may be more clearly seen in FIG. 3, the upper portion 150 is provided with a plurality of openings 154 which extend into a bore 156 which extends upwardly therethrough. The valve 152, in addition to the upper portion 150, includes an elongated stem portion 155 which extends downwardly through the passageway 88 and terminates in an enlarged portion 158. A lower stem portion 160 of smaller diameter than the elongated stem portion 155 extends through a bore 162 in the motor piston 84 and projects into the interior of the tubular extension member 74. The stem portion 160 forms a metal-to-metal seal with the bore 162. The arrangement is such that the lower stem portion 160 is exposed at one end to the pressure existing in the second passageway 96 in the interior of the tubular extension member 74 and at the other end to the pressure in the first passageway 88. As previously mentioned, the lower end 83 of the piston 84 below the sealing rings 86 is continually exposed to the relatively high fluid pressure. Due to the arrangement of the fluid motor 12, the pressure in the second passageway 96 will always be less than the pressure in the first passageway 88, therefore the second valve 152 will be urged downwardly due to the fluid pressure differential action on the stem portion 160.

'A pin 164 is connected with the enlarged portion 158 of the second pilot valve 152 and extends outwardly through the aperture 92. The other end of the pin 164 is attached to an upper extension 166 of an annular valve actuating member 168 which encircles the lower end 83 of the piston 84. The member 168 is slidable on the lower end 83 of the piston 84, to move the second pilot valve member 152 upwardly in the passageway 88.. Upward movement is imparted to the annular actuating member 168 and consequently to the second pilot valve 152 by engagement of the member 168 with the upwardly facing shoulder 32 in the header 16.

A tubular differential area main valve member 172 is slidingly disposed in the motor piston 84 generally between the first pilot valve member 108 and the sleeve 148. An upper portion 173 of the valve member 172 is slidingly disposed in the piston body and a lower portion 174 thereof is slidingly disposed within the tubular member 94.

The upper portion 173 of the differential are'a main valve 172 is provided with an annular sealing surface 176 which is engageable withthe high pressure valve seat on the first pilot valve member 108 to close the passageway 88. A second sealing portion 178 encircles the lower end of the upper portion 173 and is engageable with the lower pressure seat 102 to close the second passageway 96. The lower end of the main valve member 172 is provided with a plurality of apertures 180 which permit fluid flowing through the passageway 88 to be exerted on each end of the sleeve 148, sothat the sleeve 148 is in a balanced condition with respect to pressure in the first passageway 88, when the ports 154 and bore 156 on the second pilot valve member 152 are open.

' As can be seen in FIG. 1A, the upper end portion 173 of the main valve 172 is larger in diameter than the lower end portion 174 and is therefore subject to being moved downwardly upon application of the same pressure in the passageway 88 above and below the valve 172. The effective area of the sealing portion 178 on the main valve member 172 is less than the effective area of the lower end of the sleeve 148 for purposes which will be described hereinafter. The sleeve 148 could have been constructed as an integral extension of the tubular valve member 172. When constructed as shown, alignment and assembly problems are alleviated resulting in lower manufacturing costs. It should be pointed out that the upper portion 173 is smaller in diameter than adjacent portion 182 of the tubular body '85, thereby providing a very small annular passageway 184. The annular passageway 184 extends between the passageway 116 and the second passageway 96 by way of passageways 122 and ports 126. As will be described more fully hereinafter, this passageway 184 provides a means of initiating movement of the motor piston 84 away from the cover memher 142. The provision of the annular passageway 184 also minimizes the alignment problems which have been encountered in previously constructed pumps having a valve similar to the valve member 172.

Having described the structure of the pump unit 10 i in detail, the operation of the pump unit will now be described by reference to FIGS. 4 through 8. FIG. 8 illustrates the positions of the various parts of the fluid motor 12 during the power stroke of the motor piston 84. As illustrated, the valve ball 118 is in engagement with the seat 114, closing the passageway 116 extending through the first pilot valve member 108. A sealing portion 176 of the differential area main valve member 172 isin engagement with the high pressure annular seat 120, completely closing the first passageway 88. It can be seen that relatively high pressure fluid entering the motor cylinder 20 through the inlet port 34 will exert a force on the lower end 83 of the motor piston 84. As the fluid enters the passageway 88, it flows upwardly through the ports 154 in the second pilot valve 152, through the bore 156 therein, and into the upper portion of the passageway 88, but, as previously described, it cannot escape therefrom due to the closure of the differential area main valve member 172 and the first pilot valve member .108. With the ditferential area main valve member .172 in a position engaging the seat v120', the sealing portion 178 of the main valve member 172 will be positioned above the apertures 100, permitting fluid to flow from the upper interior of the motor cylinder 20 through the apertures 100 into the passageway 96 and thence into the interior of the tubular extension member 74. With fluid pressure applied on the lower end 83 of the piston 84, the piston will begin its upward movement in the motor cylinder 20 and fluid trapped thereabove can exhaust through the apertures 100 as described. It should be pointed out that the second pilot valve 152 cannot move relatively upwardly in the passageway 88 due to the downward force acting thereon as result of the difference in pressures in the passageways 88 and 96 as previously described.

As shown in FIG. 5, the upper end portion 90 of the motor piston 84 is in its uppermost position relative to the motor cylinder 20, thus it can be seen that the end portion 90 of the motor piston 84 never actually engages the cover member 142. The first pilot valve actuating member 128 is moved relatively downward upon engagement with the cover member 142, unseating the pilot valve ball 1118 from the seat 114. High pressure fluid from the passageway 88 may now pass through the passageway 1 16, bypassing the valve ball 118 and entering the passageways 122 to exert a downward force upon the differential area main valve member 172. The top end of the passageway 138 is effectively closed due to the engagement of the actuating member 128 with the cover member 142, thereby effectively confining the high pressure fluid passing through the passageway 116 to the passageways 122 and 128. The entrapment of the high pressure fluid results in the generation of a force opposing the relative downward movement of the actuating member 128 in the piston 84 and, as a consequence, affords a hydraulic retardation of the piston movement toward the cover member .142. As previously mentioned, the annular passageway 184 permits a small quantity of fluid to flow from the passageways 122 into the passageway 96, but such flow will not affect the hydraulic retardation of the piston 84. After the main valve member 172 has been shifted by the build up of pressure above the valve member 172, the high pressure fluid flowing through the passageway 184 into the motor cylinder 20 by way of apertures 100, will build up pressure which acts upon the upper or large end of the piston 84 to initiate the downward movement thereof. During this stage of operation of the pump unit it can-be observed that all the various parts, with the exception of those associated with the first pilot valve, remain in the same positions as described with respect to FIG. 4.

Referring briefly to FIG. 1C, the valve closure member 56 of the standing valve 46 and the valve member 80 of the traveling valve 76 are illustrated in the positions they occupy during the power stroke of the motor piston 84 as illustrated in FIGS. 4 and 5. As can be appreciated from examining FIG. 10, the valve 76 is in a closed position. As the pump piston 66 travels upwardly, fluid trapped in the pump cylinder 22 above the traveling valve 76 will be displaced upwardly and out through the outlet port 42. Simultaneously, the standing valve 46 is in the open position and fluid will be drawn in through the opening 50 of the standing valve 46 upwardly into the pump cylinder 22 below the pump piston 66 due to the negative pressure created. therein.

Very shortly after the pilot valve ball 118 is moved off the seat 114, the force exerted by the high pressure fluid in the passageways 122 will drive the differential area main valve member 172 downwardly, as shown in FIG. 6. The downward movement of the valve member 172 is arrested when the sealing surface .178 thereoncomes into sealing engagement with the low pressure annular seat 10 2, closing the second passageway 96. During the downward movement of the main valve member 172, the sealing surface 176 thereon separates from the high pressure seat 120, permitting flow from the first passageway 88 into the passageways 1 22 and the passageway 138 into the motor cylinder 20' above the piston 84 after the actuating member 130 has moved away from the cover member 142. As the high pressure fluid flows through the passageways as described, it exerts a downward force on the large, or upper, end 90 of the motor piston 84.

At this time, the relatively high pressure fluid is exerting a downward force on the upper end 90 of the motor piston 84, as well as exerting an upward force on the lower end 83 of the motor piston 84. As previously described in connection with the structure of the motor piston 84, the area of the upper end is effectively larger than the lower end 83 due to the presence of the tubular extension member 74 which extends through the packing 48. Due to this difference in effective areas, the motor piston 84 will now begin to travel downwardly in the motor cylinder 20.

Referring again to FIG. 1C, the downward movement of the motor piston 84, through use of the tubular extension member 74, will begin to drive the pump piston 66 downwardly in the pump cylinder 22. Downward movement of the pump piston 66 against the fluid which is accumulated above the standing valve 46 will create a pressure therein, closing the standing valve 46 by moving the valve closure member 56 downwardly into engagement with the seat 54. The traveling valve 76 will open to permit, the fluid in the pump cylinder 22 below the piston 66 to travel upwardly therethrough into the pump cylinder 22 above the pump piston 66.

FIG. 7 illustrates the various parts of the fluid motor 12 as the motor piston 84 reaches the end of its downward travel. As shown therein, the extreme lower end 146 of the piston 84 has entered the counterbore 30 in the header 16, providing the das'hpot arrangement as previously described. The dashpot arrangement is effective to slow the velocity of the piston 84 to prevent the piston from slamming against the header 16. The annular valve actuating member 168 has engaged the upwardly facing shoulder 32 in the header 16 to move the second pilot valve 152 upwardly in the passageway 88. Upward movement of the valve 152 moves the upper portion 150 thereof into the tubular sleeve 148, closing the ports 154, and thereby shuts off the passageway 88 through the piston 84. As shown in FIG. 7, the differential area main valve member 172 is still in the lower position, closing off the second passageway 96, as described in connection with FIG. 6. Movement of the upper portion 150 of the second pilot valve into the tubular sleeve 148, which is in engagement with the lower end 174 of the differential area main valve member 172, results in the fluid pressure in the passageway 88 being exerted on the relatively large area of the lower end of the sleeve 148. With the ports 154 of the sec-ond pilot valve 152 closed, a small amount of downward movement of the piston 84 reduces the pressure above and within the main valve 172. The provision of the aperture-s assures that the upper end of the sleeve 148 will also be exposed to the reduced pressure. As previously mentioned, the area of the sleeve 148 is larger than the area of the sealing surface 78. The differential area plus the differential pressure results in an upward force that almost instantaneously drives the sleeve 148 upwardly in the piston 84. Upward movement of the sleeve 148 carries the valve member 172 upwardly therewith until the lower end of the sleeve 1'48 passes the ports 154 of the valve 152. As soon as the sleeve 148 has cleared the ports 154 of the second pilot valve 152, the valve 152 is driven downwardly due to the differential in fluid pressure in the passageways 88 and 96. The upper end of the main valve member 1172 at this time encircles the lower end of the first pilot valve member 108 and virtually closes the flow path therebetween. The reduction in flow area creates an area of low pressure above the main valve member 172 which literally sucks the valve member 172 upwardly until the sealing surface 176 thereon engages the high pressure seat 128 (see FIG. 8). The various parts of the motor piston 84 now resume the positions as illustrated in FIG. 4 and an upward, or power, stroke of the motor piston 84 is begun.

It can be appreciated from the foregoing description that the valve actuating member 128 is pressure balanced and the only force required to move it downwardly is that force required to overcome the effect of the spring member 140 and, after engaging the ball 118, suflicient force 9 to move the ball 118 off the seat 114. Likewise, the annular member 168, which is an actuating member for the pilot valve 152, has a differential pressure exerted downwardly thereon which is equal only to the pressure differential existing in the passageways 88 and 96, and therefore, the only force required to move the valve 152 upwa-rdly is that force suflicient to overcome the small force resulting from this differential pressure.

It should be apparent from the foregoing description that a fluid actuated, reciprocating motor constructed in accordance with the invention provides a means of actuating a single acting pump which will move at a relatively high velocity during the greater part of the stroke and yet will not slam into either end of the motor cylinder. The advantage of such an arrangement is that the overall pump unit will last for an extended period of time without maintenance. Furthermore, the means utilized for changing the direction of travel of the motor piston is such that the motor piston must make an entire stroke in each direction. Also, it is virtually impossible for the motor piston to become stalled in any position due to the small amount of force needed to cause the piston to move or to change its direction from an upstroke to a downstroke, or vice versa.

It should also be pointed out that several features have been incorporated herein to reduce the manufacturing and maintenance costs and to increase the service life of the hydraulic motor. For example, the valve seat member 114 has been constructed separately so that it can be heat treated as desired and can be easily replaced. The tubula-r main valve member 2172 has a relatively large clearance in the adjacent portion 182 of the piston body, thereby alleviating some of the alignment, assembly and tolerance problems often encountered in constructing a valve for a vreciprocating fluid motor. (The differential area valve of this invention has been simplified 'by separating it into the valve member 172 and the sleeve 148. The difficulty in constructing and assembly a valve having several different diameters without misalignment can be readily appreciated.)

The embodiment described in detail herein is presented by way of example only, and it is understood that many changes and modifications can be made thereto without departing from the spirit of the invention or from the scope of the annexed claims.

What is claimed is:

1. In a fluid operated pump unit including a pump connected with and adapted to be operated by a reciprocating fluid motor and means for supplying relatively high pressure fluid to the motor, said motor comprising:

an elongated motor cylinder having a closed end, an aperture extending through the opposite end, and having the fluid supply means connected therewith adjacent said opposite end;

a differential area piston mounted for reciprocating movement in said cylinder and having a small end continually exposed to said fluid;

a tubular extension member having one end connected with the small end of said piston and extending through said aperture for connection with the pump;

said piston having a first passageway providing fluid communication therethrough from the small end to the large end of said piston, and a second passageway providing fluid communication therethrough from the large end of said'piston into said tubular extension member;

pressure responsive differential area main valve means located in said piston and adapted to open and close said first and second passageways;

first pilot valve means located near the large end of said piston and engageable with the closed end of said cylinder to open an upper portion of said first pasageway whereby fluid in said first passageway actuates said differential area main valve means to open 10 said first passageway and close said second passageway, thereby directing fluid into con-tact with the large end of said piston whereupon said piston moves in a direction away from the closed end of said cylinder; and, second pilot valve means located in the small end of said piston and engageable with the opposite end of said cylinder to close a lower portion of said first passageway whereby fluid in said first passageway actuates said differential area main valve means to close said first passageway and open said second passageway whereupon said piston moves in a direction toward the closed end of said cylinder, said second pilot valve means including a portion extending through the small end of said piston, said portion having a first area exposed to fluid pressure in said first passageway and having a second area exposed to fluid pressure in said second passageway whereby the result force on said second valve means is in a direction away from said differential area main valve means.

2. In the fluid operated pump unit of claim 1 wherein said first pilot valve means includes:

a first valve seat encircling the upper portion of said first passageway;

a valve ball disposed in said first passageway adapted for movement toward and away from said first valve seat; and,

a valve actuating memberextending from said piston comprising an elongated valve member slidingly disposed in said piston and having one end engageable with the closed end of said cylinder and the other end engageable with said valve ball to move said ball away from said valve seat upon movement of said valve actuating member after engaging the closed end of said cylinder.

3. In the fluid operated pump unit of claim 2 wherein said first valve seat also includes:

a valve seat member encircling the upper portion of said first passageway;

a separate valve seat encircling the upper portion of said first passageway and positioned in said valve seat member; and, r

a valve seat retaining member engageable with'said valve seat to prevent movement of said valve seat in said valve seat member.

4. In the fluid operated pump unit of claim 1 wherein said differential main valve means includes:

a high pressure seat disposed in said first passageway;

a low pressure seat disposed in said second passageway;

and,

a tubular valve member reciprocably mounted in said piston and encircling said first passageway, said tubular valve member having:

a large end thereof engageable with said high pressure seat to close a portion of said first passageway, a small end thereof adjacent said second valve means, and

a circumferential flange on the exterior of said tubular valve member engageable with said low pressure seat to close said second passageway.

5. In the fluid operated pump unit of claim 1 wherein said second pilot valve means includes:

an elongated member slidingly positioned in said piston,

said elongated'member having an end thereof extending into said first passageway and cooperable with said differential area main valve means to open and close said first passageway; and,

a valve actuating member connected with said elongated member and engageable with the end of said cylinder adjacent said aperture to move said elongated member, therebyclosing the lower portion of said first passageway.

close said second passageway, thereby directing fluid into contact with the large end of said piston whereupon said piston moves in a direction away from the closed end of said cylinder, said first pilot valve means including:

a first valve seat encircling the upper portion of said first passageway,

a valve ball disposed in said first passageway adapted for movement toward and away from said first valve seat, and

a valve actuating member extending from said piston comprising an elongated valve member slidingly disposed in said piston and having one end engageable with the closed end of said cylinder and the other end engageable with said valve ball to move said ball away from first valve seat upon movement of said valve actuating member after engaging the closed end of said cylinder, and,

second pilot valve means located in the small end of said piston and engageable with the opposite end of said cylinder to close a lower portion of said first passageway whereby fluid in said first passageway actuates said diflferential area main valve means to close said first passageway and open said second passageway whereupon said piston moves in a direction toward the closed end of said cylinder, said second pilot valve means including:

an elongated member slidingly positioned in said piston, said elongated member having an end thereof extending into said first passageway and coopera-ble with said differential area valve means to open and close said first passageway, and,

a valve actuating member connected with said elongated member and engageable with the end of said cylinder adjacentsaid aperture to move said elongated member, thereby closing the lower portion of said first passageway.

9. A fluid mot'or comprising:

an elongated motor cylinder having a closed end, an aperture extendingthrough the opposite end, and being adapted for connection with a fluid supply means adjacent the end having the aperture;

a differential area piston mounted for reciprocating movement in said cylinder and having a large end and a small end, said small end being continually exposed to fluid pressure;

a tubular extension member connected-with the small end of said piston and extending through said aperture;

said piston having a first passageway providing fluid communication therethrough from the small end to the large end of said piston, and a second passageway providing fluid communication therethrough from the large end of said piston into said tubular extension member;

pressure responsive differential area main valve means located in said piston and adapted to open and close said first and second passageways;

first pilot valve means located near the large end of said piston and engage-able with the closed end of said cylinder to open an upper portion of said first passageway whereby fluid in said first passageway actuates said differential area main valve means to open said first passageway and close said second passageway, thereby directing fluid int-o cont-act with the large end of said piston whereupon said piston moves in a direction away from the closed end of said cylinder; and,

' second pilot valve means located in the small end of said piston and engageable with the opposite end of said cylinder to close a lower portion of said first passageway whereby fluid in said first passageway actuates said diflerential area main valve means to close said first passageway and open said second passageway whereupon said piston movesin a direction toward the closed end of said cylinder, said second pilot valve means including: l a portion extending through the small end of said piston, said portion having a first area exposed to fluid pressure in said first passageway and having a second area exposed to fluid pressure in said second passageway whereby the result force on said second valve means is in a direction away from said differential area m-ain valve means.

10. A fluid motor comprising:

an elongated motor cylinder having a closed end, an aperture extending through the opposite end, and being adapted for connection with a fluid supply means adjacent the end having the aperture;

a differential area piston mounted for reciprocating movement in said'cylinder and having a large end and a small end, said small end being continually exposed to fluid pressure;

a tubular extension member connected with said piston and extending through said aperture;

said piston having a first passageway providing fluid communication therethrough from the small end to the large end of said piston, and a second passageway providing fluid communication therethrough from the large end of said piston into said tubular extension member;

pressure responsive differential area main valve means located in said piston and adapted to open and close said first and second passageways, said diflerential area main valve means including:

a high pressure seat disposed in said first passagea low pressure seat disposed in said second passageway, and

a tubular valve member reciprocably mounted in said piston and encircling said first passageway, said tubular valve member having a small end,

a large end engageable with said high pressure seat to close said first passageway, and

a circumferential flange on the exterior of said tubular valve member engageable with said low pressure seat to close said second passageway;

first pilot valve means located near the large end of said piston and engageable with the closed end of said cylinder to open an upper portion of said first passageway whereby fluid in said first passageway actuates said differential area main valve means to open said first passageway and close said second passageway, thereby directing fluid into contact with the large end of said piston whereupon said piston moves in a direction away from the closed end of said cylinder, said first pilot valve means including:

a first valve seat encircling the upper portion of said first passageway,

a valve ball disposed in said first passageway adapted for movement toward and away from said first valve seat, and

a valve actuating member extending from said piston comprising an elongated valve member slidingly disposed in said piston and having one end engageable with the closed end of said cylinder and the other end engageable with said valve ball to move said ball away from first valve seat upon movement of said valve actuating second pilot valve means located in the small end of said piston and engageable with the opposite end of said cylinder to close a lower portion of said first passageway whereby fluid in said first passageway actuates said differential area main valve means to close said first passageway and open said second passageway whereupon said piston moves in a direction toward the closed end of said cylinder, said second pilot valve means including:

an elongated member slidingly positioned in said piston, said elongated member having a large end thereof extending into said first passageway and cooperable with said diflerential area valve means to open and close said first passageway, a small end extending through the small end of said piston into said second passageway whereby said second valve means is .urged away from said differential area valve means by fluid pressure in said passageways, and V a valve actuating member connected with said elongated member and engageable with the end of said cylinder adjacent said aperture to move said elongated member, thereby closing the lower portion of said first passageway.

11. In a fluid motor:

an elongated motor cylinder;

a piston mounted for reciprocating movement in said cylinder, said piston having a high pressure'passage way and a low pressure passageway extending therethrough;

main valve means disposed in said piston, said main valve means being movable from a first position wherein said high pressure passageway is open and said low pressure passageway is closed to a second position wherein said high pressure passageway is closed and said low pressure passageway is open;

an elongated pilot valve slidingly supported in said piston with one end thereof extending into said high pressure passageway and the other end thereof extending into said low pressure passageway, whereby said pilot valve is continually urged toward the low pressure passageway to a first position by the difference in pressure between the high and low pressure passageways, said one end of the pilot valve being cooperable with the main valve means in a second position of the pilot valve to move the main valve means from said first main valve means position to said second main valve means position; and

means on the pilot valve engageable with the motor cylinder at one end of the movement of the piston to move the pilot valve from said first pilot valve position to said second pilot valve position against said difference in pressure.

12. In the fluid motor of claim 11 wherein the main valve means comprises a tubular main valve member having the bore therethrough forming a portion of said high pressure passageway, and wherein the pilot valve is axially aligned with the main valve means.

13. In a fluid motor:

an elongated motor cylinder;

a piston mounted for reciprocating movement in said cylinder, said piston having a high pressure passageway and a low pressure passageway extending therethrough;

main valve means disposed in said piston, said main valve means being movable from a first position wherein said high pressure passageway is open and said low pressure passageway is closed to a second position wherein said high pressure passageway is closed and said low pressure passageway is open;

first pilot valve means disposed in said piston in said high pressure passageway and having a portion thereof engageable with said motor cylinder to open said high pressure passageway whereby said main valve means is moved from said second position to said first position;

an elongated second pilot valve means slidingly supported in said piston with one end thereof extending into said high pressure passageway and the other end thereof extending into said low pressure passageway whereby said second pilot valve.me-ans is continually urged toward the low pressure passageway to a first position by the difference in pressure between the high and low pressure passageways, said one end of the second pilot valve means being cooperable with the main valve means in a second position of the second pilot valve means to move the main valve means from said first main valve means position to said second main valve means position; and,

means on the second pilot valve means engageable with the motor cylinder at one end of the movement of the piston to move the second pilot valve means from said first pilot valve position to said second pilot valve position against the action of said dilference in pressure.

References Cited by the Examiner UNITED STATES PATENTS ROBERT M. WALKER, Primary Examiner. 

1. IN A FLUID OPERATED PUMP UNIT INCLUDING A PUMP CONNECTED WITH AND ADAPTED TO BE OPERATED BY A RECIPROCATING FLUID MOTOR AND MEANS FOR SUPPLYING RELATIVELY HIGH PRESSURE FLUID TO THE MOTOR, SAID MOTOR COMPRISING: AN ELONGATED MOTOR CYLINDER HAVING A CLOSED END, AND APERTURE EXTENDING THROUGH THE OPPOSITE END, AND HAVING THE FLUID SUPPLY MEANS CONNECTED THEREWITH ADJACENT SAID OPPOSITE END; A DIFFERENTIAL AREA PISTON MOUNTED FOR RECIPROCATION MOVEMENT IN SAID CYLINDER AND HAVING A SMALL END CONTINUALLY EXPOSED TO SAID FLUID; A TUBULAR EXTENSION MEMBER HAVING ONE END CONNECTED WITH THE SMALL END OF SAID PISTON AND EXTENDING THROUGH SAID APERTURE FOR CONNECTION WITH THE PUMP; SAID PISTON HAVING A FIRST PASSAGEWAY PROVIDING FLUID COMMUNICATION THERETHROUGH FROM THE SMALL END TO THE LARGE END OF SAID PISTON, AND A SECOND PASSAGEWAY PROVIDING FLUID COMMUNICATION THERETHROUGH FROM THE LARGE END OF SAID PISTON INTO SAID TUBULAR EXTENSION MEMBER; PRESSURE RESPONSIVE DIFFERENTIAL AREA MAIN VALVE MEANS LOCATED IN SAID PISTON AND ADAPTED TO OPEN AND CLOSE SAID FIRST AND SECOND PASSAGEWAYS; FIRST PILOT VALVE MEANS LOCATED NEAR THE LARGE END OF SAID PISTON AND ENGAGEABLE WITH THE CLOSED END OF SAID CYLINDER TO OPEN AN UPPER PORTION OF SAID FIRST PASAGEWAY WHEREBY THE FLUID IN SAID FIRST PASSAGEWAY ACTUATES SAID DIFFERENTIAL AREA MAIN VALVE MEANS TO OPEN SAID FIRST PASSAGEWAY AND CLOSE SAID SECON PASSAGEWAY, THEREBY DIRECTING FLUID INTO CONTACT WITH THE LARGE END OF SAID PISTON WHEREUPON SAID PISTON MOVES IN A DIRECTION AWAY FROM THE CLOSED END OF SAID CYLINDER; AND, SECOND PILOT VALVE MEANS LOCATED IN THE SMALL END OF SAID PISTON AND ENGAGEABLE WITH THE OPPOSITE END OF 